NCIS and the Mysterious Door
by flootzavut
Summary: Winner of the NFA "Do you believe in magic?" Harry Potter crossover challenge. What will the MCRT do when a mysterious door appears in the building? Complete
1. Prologue

A/N: The title is a bit crap. Suggestions welcome.

Background knowledge of HP needed: Minimal, I hope. (So far, if the name Dumbledore means something to you, you're golden.)

_**Prologue**_

"You have to tell Gibbs."

"I'm not telling Gibbs!"

"You have to, Tim. Please?" She bit her lip.

"You tell him."

"No way. I can't tell him, he isn't gonna believe me."

"You think he's gonna believe me?"

There was a moment of silence.

"So what're we gonna do?"


	2. Chapter 1

**_GIBBS_**

Gibbs waited impatiently while the computer shut down. McGee assured him it was necessary, that just turning it off at the plug would damage it, maybe even cause him to lose files, but sitting looking at the damn thing was irritating. It was tempting just to put a bullet through it, but he'd have to work at it again tomorrow, and besides, he didn't think that Vance would take kindly to him shooting up the office equipment. He was more than ready to go home and spend a few hours working off his tension on his boat.

He didn't really register the bing of the elevator, but as soon as the door was open, Abby was barrelling out and making a beeline for his desk, with McGee trailing behind looking none too happy.

"Gibbs, Gibbs, Gibbs!"

He stifled a sigh. "What's up, Abs?"

She stopped in front of him, then turned expectantly to McGee.

Tim really did not look happy at all. "There's this... Well, it's... See, down in the evidence garage there's..."

"Spit it out, McGee."

He shrugged. "Um, Boss? I think you just better come and see..."


	3. Chapter 2

**_GIBBS_**

The door looked perfectly ordinary, not at all out of place. An ordinary metal door, slightly battered looking, with an iris scanner. To an outsider, it would've looked like it had always been there.

The problem was, a few shorts hours earlier, that particular wall had been solid brick. How a door could suddenly have materialised there - whether this constituted some sort of security risk, a truly bizarre act of terrorism, or something even more peculiar - well, that was a mystery. He was grateful he'd picked up his sidearm, even though he wasn't sure how it would help him in such a strange situation.

The three of them looked at each other. For once, Gibbs was at a loss.

"Did you try to open it?"

Abby pressed her lips together and shook her head so hard her pigtails flew out sideways.

"We thought we should wait for you, Boss," McGee explained.

Gibbs glanced around the evidence garage. At least no one else was down here to witness this... this whatever it was. He approached the door with caution. However innocent it might look, it was not supposed to be here, and while he had no truck whatsoever with anything unexplained, mysterious, or otherwise suspiciously supernatural, this was definitely outside the bounds of normality.

Cautiously, then with more confidence, he reached out to touch it. Nothing happened - that was good - but it didn't suddenly disappear, and it both looked and felt decidedly solid. That was bad. Probably.

He could feel Abby and Tim behind him, but apparently neither of them had any helpful suggestions.

There was only one obvious thing left to do. He bent down a little for the iris scanner to do its magic.


	4. Chapter 3

**_MCGEE_**

"Well, that was an anticlimax."

Gibbs turned round and glared, and Tim wished he'd kept his mouth shut.

"You try, McGee."

"Me, Boss? But if it didn't open for you, then why would it open-"

"Just do it."

He sounded exasperated, and McGee decided it was best to obey. He really didn't want to. Using an iris scanner on a door that had appeared for no reason seemed like a good way of losing an eyeball or something - it was just creepy. At least Gibbs had tried it himself first.

Tim approached the door gingerly, still half expecting it to spring open and for... something to appear. But no. It behaved exactly as a door should, as long as he ignored the fact that it seemed to have made its way into the building all by itself.

He stood in front of the iris scanner, trying to ignore the urge to blink or flee or look away. There was a quiet bleep as the machine did its thing and then... nothing.

He shrugged and stepped away, almost relieved.

Abby took a step forward. "My turn!"

"Who else is still here?" asked Gibbs.

Another beep, no open door.

McGee thought for a second. "Uh, I think Ducky is still around."

Gibbs gave him a sharp nod. "Go find him."

Just for a moment, Tim considered asking why, but Gibbs really didn't look in the mood. With a glance behind at Abby, who seemed to be trying both eyes and tilting her head to ever more peculiar angles, he scuttled off to the lift.


	5. Chapter 4

**_ABBY_**

"What you doin', Abs?"

She heaved a sigh and turned round, admitting defeat for now. "I guess I just thought it was worth a go."

Gibbs grinned a little, and she smiled back.

"Well, I had to try something, Gibbs. This is so weird."

"I thought you liked weird?"

She frowned. "I like to study weird, to figure it out and explain it. This feels..."

"Hinky?"

"Yeah. I mean... Doors don't just appear. And why have an iris scanner if no one can use it? And it looks so real..." The door seemed so innocent and so innocuous, except that appearing like it had... it was anything but. "It's freaking me out."

Gibbs looped an arm around her shoulders and gave her a squeeze. "We'll figure it out, Abs. We always do."


	6. Chapter 5

**_GIBBS_**

The door opened onto an earthen tunnel that definitely didn't look like it belonged anywhere on the Navy Yard. It was fairly bright, even welcoming, as tunnels leading into the ground go, but the flickering bluebell coloured flames that gleamed from globes hanging from the ceiling cast eerie shadows as they walked.

By the time Ducky and Jimmy had arrived, they had almost given up on the iris scanner. Gibbs had been more than ready to slap some crime tape across the door and hope to come back tomorrow and decide they'd all imagined it when, if they were lucky, it had disappeared as mysteriously as it had appeared.

No one had been more surprised than Ducky was to discover that the door opened readily when he put his eye to the scanner. Game old bird that he was, he had been ready to explore it straight away, but Gibbs had insisted that Tim get his sidearm, and that Abby perform some rudimentary tests on the air before any of them actually went through the door.

He wasn't particularly happy that of the five of them, only two were armed, and he would've liked to have Tony and Ziva with them. Letting those two go at a relatively early hour had seemed like a good idea at the time, with their most recent case put to bed, but right now he would've been very happy to have his senior agent and their resident ex Mossad assassin with them. Gibbs had done more than his share of stupid things in his lifetime, but this had to be right there in the top ten. Even so, turning back didn't seem like an option - he felt oddly compelled to keep going, despite his misgivings.

He'd reluctantly agreed that since it was Ducky whose eyes had opened the door, he was obviously a necessary member of the party. Jimmy had refused point blank to let Ducky out of his sight, and had unexpectedly shown his mettle in pure defiance.

By the time he'd got through failing to threaten Palmer into submission, one look at Abby's stubborn expression and the very firm grip she had on Tim's hand was enough for him to decide that there wasn't enough coffee in the world. Knowing Abby, she would follow them anyway given half a chance, and he'd rather keep all his non combatants together where he could see them.

He'd given McGee a glare that said that if he let anything happen to Abby, he'd regret it, and Tim had nodded firmly despite looking a little green around the gills. Message received.

The door had slid closed behind them with a faint swish, but there was an iris scanner inside too, and Ducky's eye had proven to open that one, too. At least they knew they could get out.

They'd been walking now for a good half hour, the tunnel sloping gently downwards and now finally becoming more level. Although it was easy walking and he did not feel tired, Gibbs had the strangest sensation that they were travelling much further than their actual steps. He wasn't much of a one for spooky feelings, but then, he wasn't a big fan of doors that were places they shouldn't be, either.

He glanced behind him once more, to check they were all OK, and exchanged another nod with Tim, who was bringing up the rear, then checked his watch. If they didn't find anything within the next ten minutes, he assured himself, they'd give this up, turn back, and start fresh tomorrow.


	7. Chapter 6

**_GIBBS_**

The other end of the tunnel was a door very much like the one they'd left behind them at the Navy Yard, at the top of a set of steep but neatly carved steps cut into stone. The familiarity really wasn't particularly reassuring, but at least there was a door and they had actually arrived... somewhere.

There was another iris scanner, and Ducky took the lead, standing on tiptoe to get his eye to the right height, with Gibbs beside him on the narrow flight, gun drawn.

As the door swished open, Gibbs stepped through, scanning the room beyond for potential threats. It seemed to be - well it looked a bit like an autopsy suite, though one that would have seemed more at home in one of Abby's mediaeval MMORPGs. It was lit with torches set in brackets along the walls, and the room itself was all stone and wood, with a vaulted ceiling and leaded windows. There was no real indication of where they were, and the storm battering against the windows would have made looking out pointless even if it wasn't also nighttime.

"What the...?"

They filed out into the room, looking around, trying to make sense of the strange surroundings.

Just as they had all started to breathe properly again and Gibbs had finally lowered his gun, the door swung open.

"Welcome, welcome to Hogwarts, my friends. I trust your journey was not too arduous?"

Gibbs aimed at the stranger. The man was tall and looked elderly and benign, but Gibbs wasn't one to trust appearances. Especially when the appearance was so odd. He had kindly blue eyes twinkling behind old fashioned spectacles, but was dressed in flowing robes and a pointy hat, and his air of confidence and authority suggested he was not someone to underestimate.

"What are you doing here?"

The stranger laughed. "The question, my dear Agent Gibbs, is what you are doing here. And all will be made clear in time." He nodded as if that explained everything. He was well spoken, and his accent was definitely British - maybe the idea that they had somehow walked a very long way wasn't so far fetched. "Would you like a sherbet lemon?" he added, drawing a paper bag from a pocket somewhere in his voluminous robe.

Gibbs gestured with his gun. "I'd like an explanation."

The man looked down at the weapon with an expression not of fear but of distaste. "Horrible things." He muttered something under his breath, and the gun in Gibbs' hand suddenly turned into a bunch of flowers, which he promptly dropped as if they'd bitten him. There was a collective gasp from his team members, but the stranger didn't even seem to notice.

"We should be getting on, we have things to do. Doctor Mallard! I am so glad it's you. What a pleasure, what a pleasure indeed. Please, step this way. May I call you Ducky?"

"Do I know you?"

The man shook his head vigorously. "No, no, but we do have a mutual acquaintance - a Mr Hengist Cadogan?"

Ducky frowned a little. "That's not a name I recognise..."

"Are you sure? Dear me, I must be getting ahead of myself. Careless of me, I'm sure... Well, when you do meet him, please do pass on greetings from Dumbledore."

"So... you are- Dumbledore?"

Gibbs was impressed with how calmly Ducky was taking all this. He'd always known there was more to his ME than met the eye, but after all these years Ducky could still surprise him.

"Yes, Albus Dumbledore - I'm terribly sorry, how absent minded of me to forget to introduce myself to you all. I do hope you won't think me rude, but I must hurry you. Time is of the essence."


	8. Chapter 7

**_ABBY_**

"I would ask you to keep your voices down," said Dumbledore as they went through a heavy wooden door into yet another corridor. "Most of the students will be asleep by now, and if any of them aren't I should not like to give them reason to investigate."

"Students? This is a school?" Ducky exclaimed. "Why on earth do you have an autopsy suite in a school?"

Dumbledore laughed heartily, then clapped a hand over his mouth, his eyebrows wiggling comically. "Good gracious me, that wasn't an autopsy suite. That was the Room of Requirement! I had great need of a medical examiner. I imagine the Room merely sought to provide you with the necessary equipment to fulfil my need. Though it is possible," he added in an undertone, a thoughtful expression on his face, "that the Room also wanted you to feel at home as you worked. It is quite considerate sometimes..."

He gestured towards a large picture of a fat, well dressed lady, and placed a finger over his lips. Abby couldn't imagine why they'd need to be quiet around a painting, then to her shock realised the woman in it appeared to be gently snoring.

"Wow," she murmured, and poked Tim in the side to draw his attention to it. He looked confused for a moment, but when he saw the movement and heard the quiet but very definite snores, his eyes widened.

"Curiouser and curiouser," she whispered.

As a scientist, her mind had already been working overtime trying to figure out just how Dumbledore had somehow made Gibbs' gun disappear and a bunch of roses appear. If Gibbs had been in on it, it would have been easy - but that seemed unlikely. And of course there was the initial mystery of how that door had just appeared, and how they'd walked for less than an hour only to find themselves in what appeared to be an immense castle. She was almost certain that nothing like this existed anywhere near DC.

That wasn't counting the strange things Dumbledore had said. He seemed to think the room they had arrived in could... think? She wasn't even sure she'd understood what he had implied. On top of that, they'd walked past a couple of staircases that looked uncomfortably like Escher drawings, and she'd certainly never seen an oil painting breathe before.

There was definitely something weird about it all. She couldn't help trying to make sense of it, but if there was anything or anywhere in the world that was truly inexplicable, this might be the place.

However, there was another part of her that was enthralled, delighted and fascinated. She imagined going to school in this place, maybe having someone as strange and interesting as Dumbledore for a teacher, learning... well, she couldn't even begin to guess what they might learn. She was just sure that she would enjoy it.

Despite lowering his voice, Dumbledore didn't show any sign of running out of things to say. Ducky had met his match in terms of tall tales and intriguing tangents. Even if the man had allowed them to get a word in edgewise, she doubted they'd know how to respond. So much of what he said seemed like complete nonsense: muggles, quidditch, hufflepuff. Even the words she recognised didn't help. Alchemy was long since disproven, potions were things from fairy tales, and vampires and werewolves were just legends. Weren't they? What was clear was that either Dumbledore was crazy, or there was a lot more weirdness out there than she'd come to believe.

They turned into yet another corridor and then almost ran into Gibbs when Dumbledore stopped without warning, bringing the others to an untidy halt around and behind him.

"This is our problem," he said, his voice suddenly very solemn. "Yet another Defence Against the Dark Arts teacher has fallen victim to - well, let us just say that if the subject were not so important, I should have stricken it from the syllabus." He shook his head. "Fatalities have not been the usual outcome, but nevertheless this weighs heavily on my conscience." He sighed deeply, apparently unaware that his audience was lost yet again. "When magic is the cause of death, we wizards can almost always find not only the cause, but the perpetrator. Alas, in this case, our murderer used muggle means, and thus I need your aid. I hope very much that you will be willing? Any information you can give us would be tremendously helpful."

Abby found herself nodding and murmuring yes along with the others, even as her mind grappled with his casual use of words like magic and wizard.

Ducky was still the only one of the group who seemed relatively unfazed. He had been momentarily shocked to realise this was a school, but other than that he seemed to be taking it all in his stride. She couldn't help wondering if he'd seen something in the course of his long and varied career that had made all this a little less astonishing to him than it was to the rest of them. Now he was busy examining the body, and explaining to Dumbledore what they needed to process the scene and determine what had happened.

To the surprise and wonder of the rest of the team, Dumbledore produced pencils, drawing pads, gloves, an old fashioned camera, and even a rather terrifying looking liver probe out of thin air. Ducky merely thanked him and got on with his job, ordering the others into action as if forensic autopsies in strange castles assisted by wizards were a normal part of his working life. Abby wondered whether they had been a regular occurrence at some point, and made a mental note to quiz Ducky later.

Right now, though, strange as the situation was, the most logical course of action seemed to be to do her job as best she could, and help the others do theirs. Ignoring her mind's continued insistence that she was either losing her mind or that there was something unbelievably hinky going on, she grabbed a pair of surgical gloves and, slipping them on, got down to work.


	9. Chapter 8

**_DUCKY_**

The examination of the scene and the autopsy itself were surprisingly straightforward, in the circumstances. Ducky was pleasantly surprised to discover that he had everything necessary to do his job, including equipment he didn't even have to hand in the DC morgue. Having been informed that electricity did not work in the castle, he could only imagine how some of the things worked, but the end result, no matter how peculiar some of the specifics, was that he was starting to feel quite at home.

Dumbledore had explained that this room knew what he needed and would provide it. In another circumstance Ducky might have thought that this explanation was some strange metaphor, and he still couldn't fathom exactly what the wizard meant, but it was somehow easier to accept than to try and find a logical reason for it all.

Dumbledore had been fascinated and slightly appalled by how 'muggles' (as he referred to the team) investigated a person's death. He listened and watched, and although he spent a good deal of time talking with the other members of the team, Ducky got the impression that no piece of evidence would be missed or forgotten.

Now and then, when Ducky hit a sticky spot or Jimmy had trouble retrieving something, Dumbledore mumbled a spell or swished his wand in a particular way, and as if by magic (Ducky chuckled to himself - the phrase had never been more appropriate) the problem would be resolved. By the end of the autopsy, it had almost become normal, and Ducky couldn't help thinking that a wand would make his job a good deal easier.

Eventually it was done. Although they weren't in a position to do a full criminal investigation Dumbledore assured them the information would help enormously. Despite the grisly circumstance, Ducky found himself feeling somewhat reluctant to leave. It seemed as if they had only just begun to get used to these strange but hospitable surroundings, and their host was nothing if not genial.

However a glance at his watch and the tired eyes of his colleagues reminded him that they really couldn't stay here any longer - however intriguing Hogwarts might seem. Gibbs was hovering, and Ducky could almost see the impatience on his friend's face to get back to normality._ A situation this strange and inexplicable is not Jethro's cup of tea at all... _Ducky grinned to himself - if Gibbs started drinking tea, then they would definitely have to assume they had slipped into a different reality

Dumbledore did not seem especially keen to see them go, despite his obvious desire to keep their visit hidden from the students and other staff members. However, at Gibbs' insistence he gave in gracefully, thanking them again and again for their hard work.

"All being well," he said, as they gathered around the door once more, "the Room should return you back home safely less than two hours after you left. I cannot risk you running into yourselves, but making sure you can rest before your workday begins again is the least I can do in the circumstances. My heartfelt thanks to you all." He spoke solemnly, looking at each of them in turn and nodding his thanks. "If you should ever have need of my help, be assured that I will gladly provide it. I hope to see you all return to Hogwarts some day."

After a moment of silence, the laughing twinkle returned to his eyes and he smiled broadly. "And before you leave, I should like to give you a small token of our very great appreciation and gratitude." He rummaged through his robe again and brought out a large jar filled with pale yellow sweets. "Bertie Bott's famous lemon sherbets. Believe me, they really are quite delicious."

There was a ripple of laughter at his expression, and then the door was opening, the lemon sherbets were passed to Abby, Gibbs' gun was returned to its usual shape and then to its owner, and they were saying goodbye as the door closed behind them.

They paused for a moment at the bottom of the stairs. The iris scanner had disappeared, and the door itself now looked much more like the entrance to a castle rather than an evidence locker.

Ducky glanced around at his colleagues. The eerie blue light of the tunnel made their faces look strangely pale, and each of them had an expression he felt likely mirrored his own. This had been a very, very strange evening. "Well, I suppose we had better be getting back."


	10. Chapter 9

**_MCGEE_**

McGee had never been so glad to see the evidence garage. Tonight had been a mixture of fascinating, unbelievable, and just plain hinky. It was interesting, there was no denying it, but it was good to be back safe in a world he understood. He helped Abby through the door, then hopped over the lintel himself.

"What do we do about the-"

The words died in his throat; the door had melted back into the wall, as if it had never existed.

"Guess they don't need us anymore," said Gibbs. He was glaring at the wall as if he was expecting something else to happen, but nothing did. Eventually he shrugged. "You think you've seen it all..."

"Should we tell anyone?"

"Who'd believe us, Tim?" Abby asked, and he had to concede the point.

They stood there for a few more moments. Looking around at their faces, he realised that they were all struggling with the same thought he was - _did that really just happen?_

Abby slipped an arm around his waist and he allowed her to pull him away from the place the door had been, Gibbs and Ducky behind them. Gibbs put his eye to the scanner by the elevator, and Tim wondered if he needed to reassure himself that this one, at least, still recognised his authority.

"So Duck," Gibbs asked, as the doors swooshed open and they crowded in, "that your strangest ever autopsy?"

Ducky thought for a moment. "No, actually, it wasn't. There was one case in French Polynesia, the oddest thing happened when I opened the body cavity..."

_∼FIN∽_

* * *

_**A/N: **Don't go holding your breath or anything, but there is a sequel running round my brain. Watch this space!_


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